A binding line, and particularly a so-called "saddle-stitch" binding line 10 as illustrated in FIG. 1, typically includes a number of binding-line components 12, including, for example, a gatherer, which gathers signatures to be collated into a stack in a particular order, a stitcher, which staples or stitches the stacked signatures together, and a trimmer, which trims the stitched stack of signatures to a predetermined size to produce a finished book. Binding lines typically also include a mail table on which the finished books are addressed, sorted (e.g., by zip code and/or carrier route), and bundled together for shipping. Of course, the binding line 10 can also include additional or alternative components, as desired.
FIG. 2 is a block diagram illustrating a prior-art drive system 14 for the saddle-stitch binding line 10 employing a single drive shaft 16 that mechanically links one or more drivers or motors 18 (only one of which is shown) to all components 12 of the binding line 10 such that motive power produced by the motor 18 is transmitted to all binding-line components 12 via the drive shaft 16. Even though the drive shaft 16 may actually be composite, comprising multiple drive-shaft sections 20, 22, those sections 20, 22 are permanently and mechanically linked, such as by one or more direction-changing gearboxes 24 (and/or by linear ones, not shown), so that all binding-line components 12 nonetheless remain coupled together mechanically by the single composite drive shaft 16 during all phases of operation of the binding line 10. When an operator of the binding line 10 applies "inch" or "run" commands to the motor 18 via a motor controller 26 to cause the prior-art binding line 10 of FIGS. 1 and 2 to operate at a slow speed (i.e., "inching") or at an operating speed (i.e., "running"), all components 12 of the binding line 10 operate synchronously in response to the operator's commands.
This prior-art drive system 14 is therefore disadvantageous for several reasons. First, the mechanical integrity of any binding-line drive system so diminishes as the length of the binding line increases that the accuracy of mechanical movements of binding-line components may be adversely affected. For example, inkjet printers may produce ineligible mailing labels at the mail table as a result of such inaccurate mechanical movements. Consequently, there is a practical, physical limit on the length of a binding line. Further, the substantial length of modern binding lines gives rise to electrical sensing difficulties such that measurement of an angular position of the binding-line drive shaft at one location along the length of the common drive shaft may not reliably represent the angular position at all points along the shaft. This phenomenon can cause some binding-line components to operate out of synchronization with one another.
Another disadvantage of operating all binding-line components from a common drive shaft is that some binding-line components, such as a book trimmer, for example, operate in a pulsating fashion and create periodic vibration which is transmitted to the common drive shaft and propagated along the drive shaft to other binding-line components. Such transmitted vibration can then interfere with the operation of the other binding-line components, which is highly undesirable.
Still another disadvantage is that because binding-line components coupled to a common drive shaft necessarily operate together, a binding-line make-ready or calibration procedure can be performed by only one technician at a time. Specifically, a technician performing a make-ready procedure to prepare a binding line for a particular job cannot inch or run the binding line to calibrate one component of the binding line without interfering with other technicians who might be servicing other components. Consequently, only one component of a prior-art binding line (i.e., a binding line having a single drive shaft) is calibrated or made ready at a time. This necessarily sequential make-ready/calibration procedure results in prolonged down-time for the binding line between jobs, which is costly, inefficient, and undesirable.
To enable binding lines to be made longer, prior-art binding lines comprising multiple binding-line sections have been developed. Each section has its own motor and each motor can have its own controller, or a single controller can be used to control the motors of all sections of the binding line. However, these multi-section binding lines can operate either exclusively synchronously or exclusively asynchronously, but prior-art multi-section binding lines cannot operate synchronously at some times and asynchronously at other times. Consequently, while the division of prior-art binding lines into multiple sections isolates binding-line components from vibrations transmitted from components in other sections, all sections of these multi-section binding lines must nonetheless be shut down together for make-ready if they operate synchronously. If the sections operate asynchronously and independently, they can be made ready in parallel, but significant complexity is introduced in the tracking of books between the various asynchronous segments as discussed fully in Chan, et al. U.S. Pat. No. 5,054,984, assigned to the assignee of the present application.